1. Field of the Invention
The present invention relates to a spindle motor for use in a disk drive apparatus.
2. Description of the Related Art
In recent years, in accordance with increased storage density of disks, there has been a demand for disk drive apparatuses, such as, for example, hard disk drives, to control rotation of the disks, movement of heads, and so on with higher precision. For example, in a known hard disk drive (hereinafter referred to simply as an “HDD”), a gas arranged in an interior of the HDD is a low-density gas, such as, for example, a helium gas or a hydrogen gas, and the HDD is thus arranged to achieve a reduction in resistance of the gas against a disk, a head, and so on during rotation of a spindle motor. This contributes to reducing vibration of the disk, the head, and so on, enabling highly precise data recording.
Base portions of some spindle motors (hereinafter referred to simply as “motors”) installed in HDDs are defined by portions of housings of the HDDs.
In the case where the interior of the HDD is filled with a gas such as, for example, a helium gas as described above, the helium gas, for example, which has extremely small molecules, tends to easily leak out of the interior of the HDD to an outside of the HDD. Therefore, in the case where a bearing mechanism is fixed in a through hole defined in the base portion, it may be difficult to ensure sufficient sealing of a region at which the base portion and the bearing mechanism are fixed to each other. In a known motor, as a member to achieve sealing of a gap, a rubber ball is used to prevent passing of a gas therethrough. However, when an elastic member such as a rubber member is used as a sealing member, the helium gas, for example, may leak through a slight gap between the sealing member and an edge of the through hole. Moreover, the helium gas has such a small particle size that the helium gas may pass through the rubber ball to leak out.